Investigators believe the women were sitting on the edge with their backs to the side of the train as it passed when it derailed for an unknown reason. Mayr and Nass -- students at the University of Delaware and James Madison University, respectively -- were found buried under coal, according to police.

CSX Train Derails in Ellicot City

Two dead in CSX Train Derailment (Published Tuesday, Aug. 21, 2012)

“It is tragic that we’ve lost two young women in the train derailment early this morning in Ellicott City," Gov. Martin O'Malley said in a statement. "I’ve spoken with County Executive (Ken) Ulman, and the state will continue to support our first responders and local partners in Howard County.”

Several cars in a nearby parking lot were crushed as some cars fell from the bridge. The bridge runs along the main street of the historic section of downtown Ellicott City.

Raw Video: Workers Respond to Train Derailment

On the scene of a coal train derailment in Ellicott City. (Published Tuesday, Aug. 21, 2012)

"Many of those train cars fell onto automobiles," said Howard County executive Ken Ulman. "So you have massive piles of coal and train cars on top of automobiles."

Cranes were used to remove the train cars from the vehicles, and the cars were searched for other possible victims, but none was found.

The derailment disrupted land-line service to customers, including some government clients, according to Verizon. The problems reached to the U.S. Navy base in Guantanamo Bay, Cuba. Lawyers preparing for pretrial hearings for five men charged with orchestrating and aiding the Sept. 11 terrorist attacks couldn't access information on government servers, the Associated Press reported.

The connection was restored by early afternoon but the judge granted a defense request to delay the start of the hearings 24 hours to Thursday morning. The derailment took out a cable containing fiber-optic lines suspended along a railway bridge.

Mayr and Nass both tweeted about sitting on the bridge shortly before 9 p.m. Mayr sent pictures of their feet dangling over the edge, and a view from the bridge.

Nearby residents heard the derailment. "I heard this tremendous noise," said one woman.

"It was the loudest I'd ever heard the train," said another, "and it was just straight screeching, and I thought to myself, 'It sounds like it's derailing.' My coffee table was just shaking, and I was like, 'OK, that's not normal.' This is awful."

It's not clear yet whether the train derailed because it was trying to avoid the girls on the bridge, News4's Megan McGrath reported. Satellite images from Google Maps indicate that the bridge had room on each side of the tracks.

The NTSB said Tuesday afternoon that the operator did not activate the emergency brakes. The brakes activated once the derailment began.

The train was bound for Baltimore from Grafton, W.Va.

The National Transportation Safety Board has taken over the investigation from local authorities. Officials said it likely will be a long investigation. Authorities will interview the two operators on the train and check the camera and event recorder.

Earlier Tuesday morning, a spokesperson told reporters that friends and family of Nass and Mayr had come forward to say the girls may have been on the bridge at the time of the crash. However, it took time for the bodies to be extricated from the crash and identified.

"It just looked like mass mayhem," said a witness. "It just looked like when I was a little kid, and I would just run the [toy] train off of the track, and everything went just every which way."